The present invention relates to a new and improved process for increasing the extent of afterburning of carbon monoxide (CO) formed during the decarburization of iron melts by the action of oxygen.
Carbon monoxide afterburning over a steel bath surface is well known to those skilled in the art of steel production. This CO afterburning has been necessitated in order to introduce larger charges of cooling materials such as scrap, spongy iron, etc. into the iron bath. In actual practice, additional oxygen made available over the bath by means of special blowing lances and the like. This additional oxygen acts in concert with the CO afterburning to substantially increase the amount of energy which is supplied or available to the bath.
In Luxembourg Pat. Nos. LU81,207, LU 81,853 and LU 83,354, which are assigned to the assignee hereof and are incorporated herein by reference, Applicant describes several processes wherein the amount of energy supplied or available from CO afterburning is increased. During the refining process, the liquidous slag layer floating on the bath takes on a foamy consistency. It has been shown that this foamy slag layer acts as in insulator whereby heat produced by the CO afterburning is undesirably shielded from the bath. Obviously, by preventing formation of slag foaming, an increase in heat transfer between the CO combustion and bath may be accomplished. The methods of the above referenced patents are directed at this particular problem by providing processes which inhibit the foaming of slag.
Carbon Monoxide undergoes combustion according to the formula: EQU 2CO+O.sub.2 .revreaction.2CO.sub.2 +X Joules
Unfortunately, the above chemical reaction has an equilibrium point which is significantly displaced to the left at high reaction temperatures. Since the temperatures of the iron bath are extremely high, a great deal of the CO remains unreacted (noncombusted) despite the use of a great excess of oxygen. As a consequence of this undesirable equilibrium, the CO afterburning is incomplete resulting in the CO escaping through the melting shop fireplace or smokestack. As the bath cools to lower temperatures, the equilibrium shifts and the CO easily combusts, only by this point in the refining process, the energy released by combustion is no longer helpful or necessary.